The Effect of Collisions on the Doppler Broadening of Spectral Lines

Rautian, S. G.; Sobelman, Igor I.

doi:10.1070/pu1967v009n05abeh003212

Cited by 663 publications

(245 citation statements)

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“…This kernel does not depend on the θ k angle and coincides with ab initio CMDS kernel only for θ k ≈ 90 • . This essential difference between the HC and ab initio CMDS kernels is the principal physical reason explaining why profiles originating from HC model 17,39,43,44 are not able to fully reproduce the high quality molecular spectra of self-perturbed hydrogen, see Sec. VI.…”

Section: A H2-h2 Collisionsmentioning

confidence: 99%

“…It was done by decomposing operators and functions in the Burnett basis. 19,24,25 For the purpose of this study, we assumed that correlation between phase-changing and velocity-changing collisions 16,17,[64][65][66][67] can be neglected. In this case, the collision operator can be written 53 The speed dependence of collisional broadening and shifting is described by the dimensionless functions B W (x) and B S (x), with x = v/v m the absorber reduced speed.…”

Section: B Spectral Analysismentioning

confidence: 99%

“…We quantified the systematic errors in molecular spectra analysis caused by use of oversimplified phenomenological models of velocitychanging collisions like the hard-and soft-collision (SC 36 and HC 37 , respectively) models often used in spectral line shapes analysis. 17,[38][39][40][41][42][43][44][45] .…”

Section: Introductionmentioning

confidence: 99%

“…velocity changes due to collisions, which are responsible for the Dicke narrowing effect. 7 Semi-analytical models of spectral line shapes [8][9][10][11][12][13][14] allow to include simultaneously basic effects 15 such as Doppler broadening, Dicke narrowing, 7 speed-dependent collision broadening and shifting, 16 correlation between velocity-changing and dephasing or state changing collisions 17 and nonimpact effects. 18 Ab initio line shape a) Electronic mail: piotr.wcislo@fizyka.umk.pl.…”

Section: Introductionmentioning

confidence: 99%

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Velocity-changing collisions in pure H2 and H2-Ar mixture

Wcisło

Tran

Kassi

et al. 2014

The Journal of Chemical Physics

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We show how to effectively introduce a proper description of the velocity-changing collisions into the model of isolated molecular transition for the case of self-and Ar-perturbed H 2 . We demonstrate that the billiardball (BB) approximation of the H 2 -H 2 and H 2 -Ar potentials gives an accurate description of the velocitychanging collisions. The BB model results are compared with ab initio classical molecular dynamics simulations (CMDS). It is shown that the BB model correctly reproduces not only the principal properties such as frequencies of velocity-changing collisions or collision kernels, but also other characteristics of H 2 -H 2 and H 2 -Ar gas kinetics like rate of speed-changing collisions. Finally, we present line-shape measurement of Q (1) line of the first overtone band of self-perturbed H 2 . We quantify the systematic errors of line-shape analysis caused by the use of oversimplified description of velocity-changing collisions. These conclusions will have significant impact on recent rapidly developing ultra-accurate metrology based on Doppler-limited spectroscopic measurements like Doppler-width thermometry, atmosphere monitoring, Boltzmann constant determination or transition position and intensity determination for fundamental studies.

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Section: A H2-h2 Collisionsmentioning

confidence: 99%

Section: B Spectral Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Velocity-changing collisions in pure H2 and H2-Ar mixture

Wcisło

Tran

Kassi

et al. 2014

The Journal of Chemical Physics

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“…Unlike rapidly frequency-swept techniques [8][9][10][11] , FARS does not reduce the measurement duty cycle, degrade the spectrum's frequency axis or require an unusual cavity configuration. FARS allows for a sensitivity of ∼2 3 10 212 cm 21 Hz 21/2 and a tuning range exceeding 70 GHz. This technique shows promise for fast and sensitive trace gas measurements and studies of chemical kinetics.…”

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confidence: 99%

Frequency-agile, rapid scanning spectroscopy

et al. 2013

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Challenging applications in trace gas measurements require low uncertainty and high acquisition rates [1][2][3][4] . Many cavityenhanced spectroscopies exhibit significant sensitivity and potential 5,6 , but their scanning rates are limited by reliance on either mechanical or thermal frequency tuning 7 . Here, we present frequency-agile, rapid scanning spectroscopy (FARS) in which a high-bandwidth electro-optic modulator steps a selected laser sideband to successive optical cavity modes. This approach involves no mechanical motion and allows for a scanning rate of 8 kHz per cavity mode, a rate that is limited only by the cavity response time itself. Unlike rapidly frequency-swept techniques 8-11 , FARS does not reduce the measurement duty cycle, degrade the spectrum's frequency axis or require an unusual cavity configuration. FARS allows for a sensitivity of ∼2 3 10 212 cm 21 Hz 21/2 and a tuning range exceeding 70 GHz. This technique shows promise for fast and sensitive trace gas measurements and studies of chemical kinetics.A multitude of applications have emerged that require rapid sensing of trace gas species, encompassing areas as varied as greenhouse gas monitoring 1,4,12 , breath analysis 2,13 , explosive detection 3 and chemical process monitoring. Because of their sensitivity, continuous-wave (c.w.) cavity-enhanced spectroscopies have significant potential for addressing these challenging applications 6,14,15 . However, the low mechanical or thermal tuning rates of c.w. lasers have generally limited the use of these techniques to static or slowly varying analytes. Attempts to alleviate this limitation have relied on sweeping the laser frequency [8][9][10][11] , which can compromise the fidelity of the spectrum and the instrument sensitivity 16 and reduce the measurement duty cycle. We present a new approach for cavity ring-down spectroscopy 17 in which the laser frequency is rapidly stepped to successive resonances through the use of highbandwidth electro-optics. This technique, which we refer to as frequency-agile, rapid scanning (FARS) cavity ring-down spectroscopy, allows for ultrasensitive measurements in which the acquisition rate is limited only by the cavity response. Unlike earlier techniques [8][9][10][11]18,19 , FARS allows for spectra to be recorded without any dead time due to scanning of the laser frequency, offers a metrology-level frequency axis and utilizes a conventional Fabry-Pérot resonator rather than more unusual and cumbersome cavity configurations.This frequency stepping of the probe laser is enabled by the use of a microwave driver and a high-bandwidth electro-optic modulator (EOM) to generate a series of sidebands on the probe laser (Fig. 1). We then use the cavity as a spectral filter such that only a single, selected sideband is resonant. Thus, we are able to transfer the superior switching bandwidth and precision of microwave sources into the optical domain. Ring-downs are then initiated by simply switching off the microwave frequency, thus removing the need for an acousto-...

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Diode Laser Spectrometers for Mid‐Infrared Spectroscopy

Mantz

2001

Handbook of Vibrational Spectroscopy

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The sections in this article are Introduction The Source The Optical System Line Intensity and Line Shape Measurements Tunable Diode Laser Line Shape Absorption Line Profile A Brief Summary of Some Novel Applications of Tunable Diode Lasers

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The Effect of Collisions on the Doppler Broadening of Spectral Lines

Cited by 663 publications

References 8 publications

Velocity-changing collisions in pure H2 and H2-Ar mixture

Velocity-changing collisions in pure H2 and H2-Ar mixture

Frequency-agile, rapid scanning spectroscopy

Diode Laser Spectrometers for Mid‐Infrared Spectroscopy

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